Instantons and Fluctuations in a Lagrangian Model of Turbulence

We perform a detailed analytical study of the Recent Fluid Deformation (RFD) model for the onset of Lagrangian intermittency, within the context of the Martin-Siggia-Rose-Janssen-de Dominicis (MSRJD) path integral formalism. The model is based, as a key point, upon local closures for the pressure Hessian and the viscous dissipation terms in the stochastic dynamical equations for the velocity gradient tensor. We carry out a power counting hierarchical classification of the several perturbative contributions associated to fluctuations around the instanton-evaluated MSRJD action, along the lines of the cumulant expansion. The most relevant Feynman diagrams are then integrated out into the renormalized effective action, for the computation of velocity gradient probability distribution functions (vgPDFs). While the subleading perturbative corrections do not affect the global shape of the vgPDFs in an appreciable qualitative way, it turns out that they have a significant role in the accurate description of their non-Gaussian cores.Comment: 32 pages, 9 figure

The Onset of Intermittency in Stochastic Burgers Hydrodynamics

We study the onset of intermittency in stochastic Burgers hydrodynamics, as characterized by the statistical behavior of negative velocity gradient fluctuations. The analysis is based on the response functional formalism, where specific velocity configurations - the viscous instantons - are assumed to play a dominant role in modeling the left tails of velocity gradient probability distribution functions. We find, as expected on general grounds, that the field theoretical approach becomes meaningful in practice only if the effects of fluctuations around instantons are taken into account. Working with a systematic cumulant expansion, it turns out that the integration of fluctuations yields, in leading perturbative order, to an effective description of the Burgers stochastic dynamics given by the renormalization of its associated heat kernel propagator and the external force-force correlation function.Comment: 10 pages, 6 figure

Deep learning for the classification of quenched jets

An important aspect of the study of Quark-Gluon Plasma (QGP) in ultra-relativistic collisions of heavy ions is the ability to identify, in experimental data, a subset of the jets that were strongly modified by the interaction with the QGP. In this work, we propose studying deep learning techniques for this purpose. Samples of $Z+$jet events were simulated in vacuum and medium and used to train deep neural networks with the objective of discriminating between medium- and vacuum-like jets. Dedicated Convolutional Neural Networks, Dense Neural Networks and Recurrent Neural Networks were developed and trained, and their performance was studied. Our results show the potential of these techniques for the identification of jet quenching effects induced by the presence of the QGP.Fundação para a Ciência e a Tecnologiainfo:eu-repo/semantics/publishedVersio

Identification of low energy neutral and charged cosmic ray events in large wide field observatorie

The lower energy thresholds of large wide-field gamma-ray observatories are often determined by their capability to deal with the very low-energy cosmic ray background. In fact, in observatories with areas of tens or hundreds of thousands of square meters, the number of background events generated by the superposition of random, very low energy cosmic rays is huge and may exceed by far the possible signal events. In this article, we argue that a trigger strategy based on pattern recognition of the shower front can significantly reject the background, keeping a good efficiency and a good angular accuracy (few square degrees) for gamma rays with energies as low as tens of GeV. In this way, alerts can be followed or emitted within time lapses of the order of the second, enabling wide-field gamma-ray observatories to better contribute to global multi-messenger networks of astrophysical observatories.Comment: 9 pages, 14 figure

The Constrained Conjugate Gradient Algorithm

Abstract-Based on the condition for equivalence between linearly constrained minimum-variance (LCMV) filters and their generalized sidelobe canceler (GSC) implementations, we derive the new constrained conjugate gradient (CCG) algorithm. We discuss the use of orthogonal and nonorthogonal blocking matrices for the GSC structure and how the choice of this matrix may affect the relationship with the LCMV counterpart. The newly derived algorithm was tested in a computer experiment for adaptive multiuser detection and showed excellent results

Levantamento populacional de cigarrinhas, potenciais vetoras de Xylella fastidiosa, sob condições de aumento de dióxido de carbono em plantas de café.

No Brasil, há um complexo de cigarrinhas (Hemiptera: Cicadellidae) associado à cultura do café que transmite a bactéria Xylella fastidiosa e causa a doença conhecida como ?Atrofia dos Ramos do Cafeeiro? (ARC). O experimento no sistema FACE (?Free Air Carbon Dioxide Enrichment?) consistiu de 2 tratamentos, um com aplicação adicional de CO2 (6 anéis com 200 ppmv) e o outro sem aplicação de CO2 (6 anéis). As cigarrinhas foram coletadas quinzenalmente através de uma armadilha adesiva instalada em cada um dos 12 anéis. Algumas cigarrinhas foram selecionadas para extração e amplificação de DNA. Primers específicos para detecção de X. fastidiosa e do simbionte primário - Candidatus Sulcia muelleri - foram utilizados na detecção. Em 2 anos de levantamento foram capturados 9.446 espécimes de cigarrinhas da família Cicadellidae pertencentes a 10 espécies, sendo 4.980 nos anéis com aplicação de CO2 e 4.466 nos anéis sem aplicação de CO2. Observou-se que a porcentagem de cigarrinhas positivas para X. fastidiosa foi extremamente baixa em comparação com a detecção do simbionte. O conhecimento obtido neste trabalho pode ajudar a prever os impactos das mudanças climáticas na biodiversidade de insetos, de patógenos e de simbiontes e auxiliar tanto nas técnicas de manejo integrado de pragas quanto na utilização de espécies indicadoras para efeitos de CO2